If you send an HTTP request with the header Expect set to the value 100-continue
and the server responds with an interim HTTP response with a status code of 100 and a continue handler
has been set using this method, then the handler will be called.

If you send an HTTP request with the header Expect set to the value 100-continue
and the server responds with an interim HTTP response with a status code of 100 and a continue handler
has been set using this method, then the handler will be called.